Biooxidation of hydrogen sulfide to sulfur by moderate thermophilic acidophilic bacteria.

The copper industry utilizes significant amounts of sulfuric acid in its processes, generating sulfate as waste. While sulfate-reducing bacteria can remove sulfate, it produces hydrogen sulfide (H2S) as a byproduct. This study examined the capability of a consortium consisting of Sulfobacillus thermosulfidooxidans and Sulfobacillus acidophilus to partially oxidize H2S to S° at a temperature of 45 °C. A fixed-bed bioreactor, with glass rings as support material and sodium thiosulfate as a model electron donor, was inoculated with the consortium. Formation of biofilms was crucial to maintain the bioreactor's steady state, despite high flow rates. Afterward, the electron donor was changed to H2S. When the bioreactor was operated continuously and with high aeration, H2S was fully oxidized to SO42-. However, under conditions of low aeration and at a concentration of 0.26 g/L of H2S, the consortium was able to oxidize H2S to S° with a 13% yield. S° was discovered attached to the glass rings and jarosite. The results indicate that the consortium could oxidize H2S to S° with a 13% yield under low aeration and at a concentration of 0.26 g/L of H2S. The findings highlight the capability of a Sulfobacillus consortium to convert H2S into S°, providing a potential solution for addressing environmental and safety issues associated with sulfate waste generated by the mining industry.

Isolation and characterization of a moderate thermophilic Paenibacillus naphthalenovorans strain 4B1 capable of degrading dibenzofuran from dioxin-contaminated soil in Vietnam.

A moderate thermophilic dibenzofuran (DF) degrader, strain 4B1, was isolated from dioxin-contaminated soil in Vietnam under thermophilic condition. A 16S rRNA gene sequence analysis assigned the strain to genus Paenibacillus. The optimum growth temperature of strain 4B1 was 45°C with a doubling time of 2.7 h in the presence of DF as a sole carbon and energy source. The rate of its growth and DF-degradation were approximately 3-fold higher than those of a reference Paenibacillus sp. strain. The 4B1 strain degraded 89% of 1000 mg L-1 DF within 48 h cultivation at the optimum temperature. TBLASTN analysis based on its draft genome sequence revealed that this strain possessed a dbf gene cluster. The open reading frames (dbfA1A2RBC) in the cluster shared 99-100% identity with those of Paenibacillus sp. YK5, indicating that DF was likely degraded by an angular dioxygenation pathway in strain 4B1. Four genes in the dbf gene cluster (dbfA1A2BC) were partially induced by DF, which was observed by semi-quantitative RT-PCR. Quantitative PCR analysis of dbfA1 transcripts, encoding the alpha subunit of DF dioxygenase, indicated that dbfA1 was expressed 4-times higher than that of strain YK5 at 45°C. These results suggest that the faster growth and degradation of DF in strain 4B1 could be due to differences in transcriptional regulation of dbf cluster genes.

Identificação de micro-organismos presentes em sistemas de biolixiviação de cobre a 35 e 50°C / Identifying microorganisms related to copper bioleaching at 35 and 50°C

RESUMO A biolixiviação de minérios de baixo teor e com elevado conteúdo de impurezas tem se mostrado alternativa importante para o aproveitamento destes, uma vez que a recuperação do metal por métodos pirometalúrgicos convencionais mostra-se economicamente inviável. A identificação e quantificação dos micro-organismos capazes de promover a biolixiviação mostram-se estratégicas para alcançar bons rendimentos no controle do processo e na recuperação de metais. Nesse sentido, as técnicas de biologia molecular são as ferramentas mais utilizadas para tal propósito. Este trabalho, utilizando técnicas de reação em cadeia da polimerase (PCR), polimorfismos de comprimento dos fragmentos de restrição (RFLP) e reação em cadeia da polimerase seguida de eletroforese em gel com gradiente desnaturante (PCR-DGGE), mostrou que a diversidade nas colunas de biolixiviação de cobre estudadas é baixa e que a temperatura é importante na manutenção de determinadas espécies, havendo predominância de Acidithiobacillus ferroxidans a 35°C e de Sulfobacillus thermosulfidooxidans a 50°C.

ABSTRACT Bioleaching is an alternative to pyrometallurgy for the production of metals from low-grade ores containing high level of impurities, once that live pyrometallurgical methods are economically unfeasible. The quantification and identification of those microorganisms related to bioleaching is an important strategy for process control and thus metal recovery. In this regard, molecular biology is one of the main techniques utilized for such objective. This study applied PCR, RFLP and PCR-DGGE techniques to show that the microbial diversity in copper bioleaching columns under investigation is low and the temperature is important to define the species found, with predominance of Acidithiobacillus ferroxidans, at 35°C and Sulfobacillus thermosulfidooxidans at 50°C.

Complete genome sequence of Oceanithermus profundus type strain (506).

Oceanithermus profundus Miroshnichenko et al. 2003 is the type species of the genus Oceanithermus, which belongs to the family Thermaceae. The genus currently comprises two species whose members are thermophilic and are able to reduce sulfur compounds and nitrite. The organism is adapted to the salinity of sea water, is able to utilize a broad range of carbohydrates, some proteinaceous substrates, organic acids and alcohols. This is the first completed genome sequence of a member of the genus Oceanithermus and the fourth sequence from the family Thermaceae. The 2,439,291 bp long genome with its 2,391 protein-coding and 54 RNA genes consists of one chromosome and a 135,351 bp long plasmid, and is a part of the Genomic Encyclopedia of Bacteria and Archaea project.